1. Field
This application relates generally to wireless communication and more specifically, but not exclusively, to circuit switched fallback procedures.
2. Introduction
A wireless communication network may be deployed over a defined geographical area to provide various types of services (e.g., voice, data, multimedia services, etc.) to users within that geographical area. In a typical implementation, access points (e.g., corresponding to different cells) are distributed throughout a network to provide wireless connectivity for access terminals (e.g., cell phones) that are operating within the geographical area served by the network.
In general, at a given point in time, an access terminal will be served by a given one of these access points. As the access terminal roams within a given cell associated with a current serving access point, signal conditions at the access terminal may change, whereby the access terminal may be better served by another access point. Consequently, the access terminal may be handed-over from its serving access point to the other access point to maintain mobility for the access terminal.
In addition, in some cases an access terminal on a packet switched (PS) network may need to be handed over or redirected to a circuit switched (CS) network. For example, some types of wireless networks are exclusively packet switched networks, whereby all traffic is routed through the core network via packets (e.g., Internet Protocol (IP) packets). However, some types of access terminals may support packet switched connectivity (e.g., for multimedia data) and circuit switched connectivity (e.g., for voice calls and Short Message Service (SMS) communication). Accordingly, a packet switched network may support handing-over or redirecting an access terminal to CS radio access technology (RAT). As a specific example, 3GPP evolved packet system (EPS) supports a CS fallback (CSFB) procedure that enables the provisioning of voice and other CS domain services (e.g., SMS) by reuse of CS infrastructure for an access terminal served by Evolved UMTS Terrestrial Radio Access Network (E-UTRAN). Thus, a CS fallback-enabled terminal initially connected to E-UTRAN may use a CS fallback procedure to access a CS domain (e.g., a 2G or 3G network) via GSM EDGE Radio Access Network (GERAN), UTRAN, cdma2000 RAN, or some other RAT.
Under certain circumstances, handover of an access terminal may be invoked during a CS fallback procedure. Accordingly, there is a need for effective techniques for handing CS fallback under these and other circumstances.